Resistance element



Dec. 3, 1929.

w. B. svnrs RES I STANCE ELEMENT Filed June 50, 1928 Patented Dec. 3, 1929 WYTZE BENE SMITS, F KASSEL-WILHELMSHOHE, GERMNY RESISTANCE ELEMENT Application led J'une 30, 1928, Serial No. 289,477, and in Czechoslovakia February 23, 1928.

is the efficiency of the resistance unit, and the firmer this layer of insulation is enclosed by the layer of metal, the better the transfer of heat that is obtained. f

Because however the winding together with the insulation is in most cases applied on cores such as metal pipes or on plates, these metal pipes or plates` which are cast or pressed, a mass of metal, must -afterwards be closed up air-tight and acid-tight. In order to obtain this air-tight and acid-tight closure, a pipe 2 having both of its ends flared at anangle of approximately 45 is used.

In case the pipe material has a coefficient of expansion different from that'of the mass of metal, the tightening or sealing will be exactly the same as when the materlal of the mass of metal would have the same coeticient 30 of expansion as the pipe-metal and this is due to the fact that the ends of the pipes are widened or ared at an angle of about 45.

In the drawing: i Fig. 1 is a view illustrating one embodiment of the invention, and v Fig. 2 is a view illustrating another em bodiment of the invention.

In Fig. 1 the numeral 1 indicates the copper terminal, which goes through the pipe 2. The pipe 2 serves as a support for the resistancewires 3. The whole is enclosed by a mass of metal 4 cast thereon. After the pipe 2 has been enclosed by the mass of metal 4, which has a coetlicient of expansion different from that of the pipe 2, the following shrinking` process results.A

On thesurfaces 5 and 6 of the ends of the pipe which ends, through widening, are fiared to project beyond the circumference of the pipe, the metal, after the casting step, has

become connected with the enlarged ends of the pipe and the direction of the shrinking pressure is indicated by the reference letter R. When the resistance'unit, thus produced, is now installed in the electric circuit and the circuit is closed, current fiows' through the vwinding 3, which becomes heated to a comparatively high degree. Thereupon the heat of the winding 3 is transferred to the pipe 2 and the mass of metal 4.

In the event the metal expands to the same degree as the pipe 2, the shrinking-pressure resulting from the casing operation, continues to exist and the unit remains closed or sealed.

In the event the pipe expandsto a less'de- ,65 gree than the cast covering or enclosing material, the mass of metal will creep or shift in' the direction of the arrows B, so that the secure sealing of the covering remains exactly the same as before.

In the event the pipe expands to a degree .greater than the cast covering or enclosing material, the pipe receives a counter-pressure in the direction of the arrows R, sothat the secure sealing of the covering remains exact'- 75 ly the same as before.

Thron h this method of assembling and sealing t e parts, of the unit, therefore, an air-tight and acid-proof sealing of the unit is obtained, whereby the resistance-wires situso ated in the interior are fully protected.

The same result is obtained by the ar.- rangement shown in Fig. 2, in which form of the invention, the enlarged ends of the p-ipe, instead of being flared at an angle of 45 are,I 85 by a further` bending formed to extend at a' right angle.`

Claims:

1. An electrical heat resistance unit comprising insulated resistance wires, a metal core 9o about which said wires are wound, and a metallic enclosure cast about the core and resistance wires, the ends of the core being outwardly directed whereby a seal will be maintained between the parts upon expansion or contraction of the core and enclosure.

2. An electrical heat resistance unitlcomprising insulated resistance wires, a metal core about which `said wires are wound, and a metallic enclosure cast about the core and resistance Wires, the core having conically flared ends.

3. An electrical heat resistance unit comprising insulated resistance wires, a tubular' 5 metal core about which said Wires are wound,

and a metallic enclosure cast about the core and resistance Wires, the ends of the tubular core 'being overturned outwardly, substantially at rlght angles.

In testimony whereof I have signed my name to this specification.

WYTZE BEYE SMITS. 

